Libraries

C Syntax

FORTRAN Syntax

Description

The gselect subroutine puts the system in
selecting mode. In this mode, the system notes when a drawing routine intersects the selecting volume and writes the contents of the
name stack to the specified buffer.

If you push a name onto the name stack just before you call each drawing routine, you can record which drawing routines intersected the selecting region. Use the current viewing matrix to define the selecting region.

The gselect and pick subroutines differ only in the manner in which the pick or select volume is specified. The pick subroutine uses a volume (default 10x10 pixels) centered on the current cursor location, while the gselect subroutine uses the unit cube (1x1x1) in modeling coordinates, thus employing the current viewing matrix in determining the selecting volume.

Nothing is drawn to the screen when the system is in selecting mode. Instead, drawing commands are piped to the select mechanism and used to determine the pick or select region hits.

With one exception, all drawing routines cause hits, including clear, points, lines, polygons, arcs, circles, curves, patches, and NURBS. The charstr subroutine does not cause a hit, although cmov and cmov2 do cause hits.